This invention relates to air control valves such as used, for example, in irrigation systems and is an improvement of the vacuum relief valve component disclosed in my U.S. Pat. No. 3,766,941.
In fluid flow lines such as found in irrigations systems, for example, one of the problems encountered relates to the creation of certain vacuum conditions which adversely affect the efficient operation of the entire system when the flow is periodically shut down and restarted. Such systems generally include valved capped riser pipes at selected intervals which, when the system is shut down, open to permit the entrance of air from the atmosphere for preventing a vacuum build up in the riser pipe and which, when the system is started up with the air in the riser pipe being compressed by the rising fluid, closes in response to such air pressure and at the same time with air escaping to the outside while the valve is closing. Such type of a valved cap is disclosed in my patent identified above.
It has now been determined from experiments and experience that upon the starting up of the system, the cap valve frequently reaches its closed position prior to the time all of the air in the riser pipe is expelled so that the trapped air, together with additional air being added by operation of the pump, generates pressures with resulting well known hammering and pounding effects that can and do seriously damage the system.
Accordingly, with the above observations in mind, it is one of the important objects of this invention to provide an improved air removal valve structure in the riser pipe of a fluid flow system which assures the complete exhaustion of air present in such pipe at the time such system is turned on and normally closes the valve in such pipe.
Another object herein is to provide an air valve of the above class which has primary valve means to the outside atmosphere when the system is shut down which closes when the system is started up and which includes auxiliary air removal means by which air that may still be trapped in the riser pipe after the valve is closed in its normal manner, is provided with a novel alternate escape path to the outside atmosphere.
More particularly it is an object herein to provide an air removal valve as characterized which includes an elongated flexible air vent hose or conduit in communication at one end with the upper section of the riser pipe and extending into the main flow line in the direction of flow whereby in the operation of the system, a suction is created in the air conduit to exhaust air in the riser pipe into the main fluid flow for expulsion at a main line outlet.
The foregoing objects and such further objects as may appear herein, or be hereinafter pointed out, together with the advantages of this invention will be more fully discussed and developed in the more detailed description of the accompanying drawings.